Polytrimethylene ether glycol and its uses have been described in the art. Preferred methods for preparation of polytrimethylene ether glycol involve acid catalyzed polycondensation of 1,3-propanediol. For example, U.S. Pat. No. 6,720,459 and U.S. Pat. No. 6,977,291 disclose processes for preparation of polytrimethylene ether glycol from 1,3-propanediol using a polycondensation catalyst, preferably an acid catalyst.
WO99/01496 discloses a process for the purification of polyethers including the steps of (a) heating a polyether glycol with water for a time and at temperature sufficient to substantially hydrolyze esters formed during polymerization, (b) separating the polyether from the water, and (c) subjecting the polyether recovered from step (b) to further washing with hot water to remove residual acid.
U.S. Pat. No. 6,977,291 describes a purification procedure for crude polytrimethylene ether glycol obtained from an acid catalyzed polymerization process comprising (1) a hydrolysis step to hydrolyze the acid esters formed during the acid catalyzed polymerization, (2) phase separation and water extraction steps to remove the soluble acid catalyst, generating an organic phase and a waste aqueous phase, (3) a base treatment of the organic phase to neutralize and precipitate the residual acid present, and (4) drying and filtration of the polymer to remove residual water and solids. It is clear from U.S. Pat. No. 6,977,291 that, when sulfuric acid is used as a catalyst to make polyether glycols from their corresponding diols, it is preferred to include a hydrolysis step because a substantial portion of the acid is converted to the ester (alkyl hydrogen sulfate). These ester groups act as emulsifying agents during the water washing process, thus causing the washing process to be difficult and time consuming, and causing incomplete acid removal. The hydrolysis step is also important in order to obtain polymer with the high dihydroxy functionality required to use the polymer as a reactive intermediate. When the hydrolysis step is incorporated into the process, it is generally found that the phase separation between the water and polytrimethylene ether glycol phases can take a substantial amount of time, e.g., up to about 35-40 hours. Consequently, there is a need for a method to reduce the phase separation time.
US2005/0272911A1 and U.S. Provisional Application No. 60/761,291 (filed Jan. 23, 2006, entitled PROCESS FOR PRODUCING POLYTRIMETHYLENE ETHER GLYCOL) disclose polycondensation processes for preparing polyether polyols, including preparing polytrimethylene ether glycol from 1,3-propanediol, utilizing a polycondensation catalyst system that contains both an acid and a base. It is disclosed that the use of this catalyst system produces polyether polyol with high degree of polymerization and low color under mild conditions. The purification processes utilize a hydrolysis step wherein water and organic solvent that has affinity for both water and the polyether polyol are used and subsequent separation into aqueous and organic phases. In one example of US2005/0227911A1, there is disclosed the use of calcium hydroxide to treat the organic phase after the phase separation.
The disclosures of all of the above-identified publications are incorporated by reference herein for all purposes as if fully set forth. Commonly owned U.S. patent application Ser. No. 11/204,731 (filed Aug. 16, 2005) (the disclosure of which is incorporated by reference herein for all purposes as if fully set forth) relates to a process of manufacture of polytrimethylene ether glycol comprising: (a) polycondensing reactant comprising diol selected from the group consisting of 1,3-propanediol, 1,3-propanediol dimer and 1,3-propanediol trimer or mixtures thereof in the presence of acid polycondensation catalyst to form polytrimethylene ether glycol; (b) adding water to the polytrimethylene ether glycol and hydrolyzing the acid esters formed during the polycondensation to form a hydrolyzed mixture containing the polytrimethylene ether glycol and the hydrolyzed acid esters; (c) adding organic solvent that is miscible with water to the hydrolyzed mixture to form an aqueous-organic mixture comprising (i) organic phase containing polytrimethylene ether glycol and residual acid polycondensation catalyst from the polycondensing and (ii) water phase; (d) separating the water phase and the organic phase; (e) adding base to the separated organic phase to neutralize the residual acid polycondensation catalyst by forming salts of the residual acid polycondensation catalyst; (f) separating the organic phase into (i) liquid phase comprising the polytrimethylene ether glycol, the organic solvent and any residual water, and (ii) solid phase comprising the salts of the residual acid polycondensation catalyst and the base which is unreacted; and (g) removing the organic solvent and the residual water from the organic phase to obtain polytrimethylene ether glycol.
Commonly owned U.S. patent application Ser. No. 11/204,713 (filed Aug. 16, 2005) (the disclosure of which is incorporated by reference herein for all purposes as if fully set forth) discloses a process of manufacture of polytrimethylene ether glycol that is similar to that disclosed in previously incorporated U.S. patent application Ser. No. 11/204,731 (filed Aug. 16, 2005), except that an organic solvent that is miscible with polytrimethylene ether is added to the hydrolyzed aqueous mixture.
Both previously incorporated U.S. patent application Ser. No. 11/204,713 (filed Aug. 16, 2005) and Ser. No. 11/204,731 (filed Aug. 16, 2005) disclose that the addition of solvent to the hydrolyzed aqueous mixture promotes rapid separation of the water and organic phases. It would be highly desirable to have a process that promotes the rapid separation the water and organic phases yet minimizes or even avoids the use of organic solvents. The present invention describes such a process.